1907> vas discussed Ijy Schott (1908), while the other set, obtained 

 in September of both I9IO and I9II, "was described by Schulz ( 191^1 ) . 

 The third set was taken by Blegvad (19UU) in March and April, 1937, 

 and February, March, and April, 1938 • Although the data are less 

 complete than our records for August, they yield interesting compar- 

 isons. The sketchy information for the Gulf of Oman and most of the 

 Strait of Hormuz shovs that the salinity is fairly constant from 

 February through September. In the Persian Gulf during all four sea- 

 sons the salinity increases from northeast to southwest across the 

 Gulf, although on the basis of scantier information Schott (l9l8b) 

 indicated an increase in the opposite direction for late winter and 

 early fall. No very great seasonal variation appears to exist in 

 the southeastern half of the Gulf, but the condition is different 

 in the northwestern half. A comparison of the four sets of isohalines 

 shows that over much of the latter area the salinity for the February- 

 March-April period was between koXo and 4lXo , whereas for the May- 

 June period it was between 39Xo and 40^ , and for August it was mostly 

 between 3^%" and 39^° > hut for September it rose again to 39^ "to 

 kO%o . Thus, it appears that the salinity during winter is greater 

 than in summer. Schott (1908) considered this condition to result 

 from variation in flow of fresh water through the Shatt al Arab. He 

 stated that the flow is least from September to November and that in 

 December local rainfall causes an increase, and the discharge con- 

 tinues rather high through January, February, and March. In April 

 the melting snow of the Armenian mountains causes another increase 

 that finally reaches a high point in May and June . In July the river 

 discharge falls again. The high salinity in the northwestern half 

 of the Gulf may also be controlled by variation in the rate of evap- 

 oration. When the temperature of the air is greater than that of 

 the water, as during the summer, evaporation from the sea is at a 

 minimum. During the winter the air is colder than the sea, so evap- 

 oration is greater then .... Thus, the annual variation of evap- 

 oration exerts a seasonal control on surface salinity that is nearly 

 parallel with the control by variation of runoff." 



Sections of temperature and salinity for the Persian Gulf for 

 August prepared by K. 0. Emery are shown in Figure 17-3. 



40 



